Absorbent articles such as sanitary napkins, pantiliners, tampons, absorbent interlabial devices, disposable diapers, incontinence products, and bandages are designed to absorb and retain liquid and other discharges from the human body and to prevent body and clothing soiling.
In the manufacture of absorbent articles, it is generally necessary to bond the components that will form the absorbent article together in order to form the finished product. Typical methods for bonding such material include adhesives, heat and/or pressure, and ultrasonics.
Some materials, however, cannot be bonded by these typical bonding techniques because of their structural integrity or composition. One such type of material are absorbent foam materials made from high internal phase emulsions (or “HIPE” foams) such as those described in U.S. Pat. No. 5,260,345 issued to DesMarais, et al. on Nov. 9, 1993; U.S. Pat. No. 5,268,224 issued to DesMarais, et al. on Dec. 7, 1993; and U.S. Pat. No. 5,387,207 issued to Dyer, et al. on Feb. 7, 1995. Such materials typically have a low tensile strength and/or low structural integrity. It is difficult to bond to such materials using adhesives because the structural integrity is often not as strong as the adhesive bond. As a result, only the portions of these materials that are in direct contact with the adhesive will remain bonded to other materials. The remainder of the material will readily separate from the material to which it is bonded. Such materials cannot be bonded using heat bonds because such foams are thermoset polymers. Once they are formed, they cannot be remelted. Instead, when heat is applied to such foam materials, they will char rather than melt and flow, which is needed for heat bonding. Such foam material likewise cannot be pressure bonded since the thermoset foam material has no ability to flow and be fused under pressure.
U.S. Pat. No. 4,473,611 entitled “Porous Polymeric Material Containing a Reinforcing and Heat-Sealable Material” issued to Haq on Sep. 25, 1984 describes one prior effort to bond materials to a highly porous polymeric material prepared by polymerization of a high-internal phase emulsion. The Haq reference discloses providing such a material with the ability to form heat seals by incorporating thermoplastic fibrous, particulate, or foraminous material therein. An article such as a wipe is formed by sandwiching the modified porous polymeric material between two heat sealable substrates, and heat sealing the first and second substrates to the heat-sealable reinforcing material in the intermediate highly porous polymeric material. The method of making the porous polymeric material described in the Haq patent, however, requires the addition of thermoplastic material. This complicates the process of making the porous polymeric material.
Other types of materials used in the manufacture of absorbent articles frequently comprise thermoplastic materials. U.S. Pat. No. 4,854,984 entitled “Dynamic Mechanical Bonding Method and Apparatus” issued to Ball, et al. on Aug. 8, 1989 discloses a method and apparatus for dynamically mechanically bonding together a plurality of laminae by feeding the laminae through a pressure biased nip between a pair of rolls, at least one of which has a relief pattern thereon. The method described in the Ball, et al. patent has been used with great commercial success. Still, the search for improved methods of bonding materials has continued.
Thus, a need exists for improved methods of bonding materials, especially those used in absorbent articles. For example, a need exists for an improved method of bonding materials for use in absorbent articles that cannot be bonded by known bonding techniques, and in particular for a method that does not require the addition of thermoplastic materials to the material in issue in order to bond other materials thereto. A need also exists for a method of bonding through relatively thick materials during the manufacture of absorbent articles. In addition, a need also exists for methods of bonding which are able to create a virtually unlimited number of bonding patterns in the materials to be bonded.